Soybean is an important crop and is a primary food source in many areas of the world. The methods of biotechnology have been applied to soybean for improvement of agronomic traits and the quality of the product. One such quality trait is a soybean oil comprising altered fatty acid levels.
It would be advantageous to be able to detect the presence of transgene/genomic DNA of a particular plant in order to determine whether progeny of a sexual cross contain the transgene/genomic DNA of interest. In addition, a method for detecting a particular plant would be helpful when complying with regulations requiring the pre-market approval and labeling of foods derived from the recombinant crop plants.
Soybean oils have been modified by various breeding methods to create benefits for specific markets. However, a soybean oil that is broadly beneficial to major soybean oil users such as consumers of salad oil, cooking oil and frying oil, and industrial markets such as biodiesel and biolube markets, is not available. Prior soybean oils were either too expensive or lacked an important food quality property such as oxidative stability, good fried food flavor or saturated fat content or an important biodiesel property such as appropriate nitric oxide emissions or cold tolerance or cold flow.
Soybean oil typically contains approximately 20% oleic acid. Oleic acid has one double bond, but is still relatively stable at high temperatures, and oils with high levels of oleic acid are suitable for cooking and other processes where heating is required. Recently, increased consumption of high oleic oils has been recommended, because oleic acid appears to lower blood levels of low density lipoproteins (“LDLs”) without affecting levels of high density lipoproteins (“HDLs”). However, some limitation of oleic acid levels is desirable, because when oleic acid is degraded at high temperatures, it creates negative flavor compounds and diminishes the positive flavors created by the oxidation of linoleic acid. Neff et al., JAOCS, 77:1303-1313 (2000); Warner et al., J. Agric. Food Chem. 49:899-905 (2001). It is thus preferable to use oils with oleic acid levels that are 65-85% or less by weight, in order to limit off-flavors in food applications such as frying oil and fried food. Other preferred oils have oleic acid levels that are greater than 55% by weight in order to improve oxidative stability.
For many oil applications, saturated fatty acid levels of less than 8% by weight or even less than about 2-3% by weight are desirable. Soybean oil typically contains about 16-20% saturated fatty acids: 13-16% palmitate and 3-4% stearate (see generally Gunstone et al., The Lipid Handbook, Chapman & Hall, London (1994)). Saturated fatty acids have high melting points which are undesirable in many applications. When used as a feedstock or fuel, saturated fatty acids cause clouding at low temperatures and confer poor cold flow properties such as pour points and cold filter plugging points to the fuel. Oil products containing low saturated fatty acid levels may be preferred by consumers and the food industry because they are perceived as healthier and/or may be labeled as “saturated fat free” in accordance with FDA guidelines. In addition, low saturate oils reduce or eliminate the need to winterize the oil for food applications such as salad oils. In biodiesel and lubricant applications oils with low saturated fatty acid levels confer improved cold flow properties and do not cloud at low temperatures.
Soybean lines that produce seed with mid-oleic and low saturate content would be desirable. Methods disclosed here enable production of soybean seeds that have oleic acid levels in the mid oleic range of 55-80% and saturated fatty acid levels of less than 8%.
The expression of foreign genes in plants is known to be influenced by their chromosomal position, perhaps due to chromatin structure (e.g., heterochromatin) or the proximity of transcriptional regulation elements (e.g., enhancers) close to the integration site (Weising et al., 1988 Ann. Rev. Genet 22:421-477). For this reason, it is often necessary to screen a large number of events in order to identify an event characterized by optimal expression of an introduced gene of interest. For example, it has been observed in plants and in other organisms that there may be wide variation in the levels of expression of an introduced gene among events. There may also be differences in spatial or temporal patterns of expression, for example, differences in the relative expression of a transgene in various plant tissues, that may not correspond to the patterns expected from transcriptional regulatory elements present in the introduced gene construct. For this reason, it is common to produce several hundred to several thousand different events and screen the events for a single event that has the desired transgene expression levels and patterns for commercial purposes. An event that has the desired levels or patterns of transgene expression is useful for introgressing the transgene into other genetic backgrounds by sexual outcrossing using conventional breeding methods. Progeny of such crosses maintain the transgene expression characteristics of the original transformant. This strategy is used to ensure reliable gene expression in a number of varieties that are suitably adapted to specific local growing conditions.
It is possible to detect the presence of a transgene by any well known nucleic acid detection method such as the polymerase chain reaction (PCR) or DNA hybridization using nucleic acid probes. These detection methods generally focus on frequently used genetic elements, such as promoters, terminators, marker genes, etc. As a result, such methods may not be useful for discriminating between different events, particularly those produced using the same DNA construct unless the sequence of chromosomal DNA adjacent to the inserted DNA (“flanking DNA”) is known. An event-specific PCR assay is discussed, for example, by Taverniers et al. (J. Agric. Food Chem., 53: 3041-3052, 2005) in which an event-specific tracing system for transgenic maize lines Bt11, Bt176, and GA21 and for canola event GT73 is demonstrated. In this study, event-specific primers and probes were designed based upon the sequences of the genome/transgene junctions for each event. Transgenic plant event-specific DNA detection methods have also been described in U.S. Pat. Nos. 6,893,826; 6,825,400; 6,740,488; 6,733,974; 6,689,880; 6,900,014 and 6,818,807.
This invention relates to the transgenic soybean (Glycine max) plant MON87705 with an oil composition comprising altered fatty acid levels and to the DNA construct of soybean plant MON87705 and the detection of the transgene/genomic insertion region in soybean MON87705 and progeny thereof.